Hi Stefan,

     I think you are advocating higher voltage and lower current to decrease loss in the FET due to the on resistance which is a good idea.

But  what I am looking for is for  over-current protection which would be valuable in any class-D design regardless of the choice of FETs. As Alan has pointed out the wrong output impedance can cause the amp to draw large currents. I am now using a current sense resistor but I was thinking that Hall Effect might be more efficient.

73 Warren

On Tue, Apr 9, 2013 at 8:27 AM, Stefan Schäfer <[email protected]> wrote:

Hi Warren,

Instead of spending to much effort to the current sensing my advice is to use other FETs. A 500 V FET at 30 V supply voltage is a heavy waste of power in the on resistance. For 30 V and a class D, try e.g. a IRFP3710 or IRFP150N . That should work much better.

73, Stefan/DK7FC